The present invention relates to the full-scope real-time simulation of the dynamic operation of a nuclear powdered electrical generating plant for training plant operators.
The increasing demand for well trained power plant operators together with the complexity of modern day power plants, has led to the realization that the simulator is the nost effective tool for such training.
Also, with advancements in nuclear power plant technology, experienced opertors from time-to-time need retraining in order to be competent. An actual nuclear plant cannot provide the operator with the required experience, such as starting up, changing load, and shutting down, for example, except after years of experience; and even then it is unlikely that he would observe the effect of important malfunctions and be able to take the best corrective procedures.
Although simulators have been used for many years, in power plant design, it is only recently that they have been used for power plant operator training. An article in the July 22, 1968 issue Electrical World, entitled "Nuclear Training Center Using Digital Simulation" briefly describes the installation of a boiling water reactor plant simulator. An article in the same publication in the Oct. 6, 1969 issue entitled "Huge Simulator to Ready More Reactor Operators" discusses the proposed installation of a pressurized water reactor simulator. In Volume 10, No. 5 of the publication "Nuclear Safety" published during September and October 1969 is an article entitled "Training Nuclear Power Plant Operators With Computerized Simulators", and in the June 1972 issue of the publication "Power Engineering" there is an article entitled "Simulators" which describes a number of power plant operator training simulators presently in use or proposed.
Design simulators usually cover only a small part of the process, and may run slower or faster than real-time; while training simulators must operate and respond in a manner identical to the actual plant. A design simulator may involve only a narrow range of conditions, while a training simulator must simulate from "cold" shutdown to well beyond normal operating conditions. A design simulator usually involves only the major process, while a training simulator should cover every auxiliary system with which the plant is concerned.
Training simulators presently in use for operator training, which are more or less complete in their simulation utilize a digital computer that is connected to control consoles that are identical in operation and appearance to the plant being simulated. Also, an instructor's console is connected to control the simulator, introduce malfunctions, initialize the simulated plant at selected states of operation, and perform other functions useful for training purposes and control of the simulator. These computers have been of the same type used for aircraft training in some instances, and process control in another.
Full-scope simulators, which involve the entire range of operation under normal, abnormal and emergency conditions; and simulate the entire plant from the reactor to the generator including all the auxiliary systems, involve in the neighborhood of from four thousand to five thousand contact inputs and outputs, and require thousands of calculations every fraction of a second. Thus, the system and organization for handling the data becomes of paramount importance.
More specifically, a training simulator, include control consoles that include levers, switches, and pushbuttons identical to those that operate remotely the control devices of the plant; and includes indicating lights, meters, pen recorders, and other devices for monitoring the physical condition of the plant.
In actual training programs, the simulator is first "initialized"; that is, the meters on the control board and the physical values in the digital computer are set for a certain steady-state condition of the entire plant. At the end of a training session the computer is shut off, or may be reinitialized to a different set of conditions for another training class. Each time it is initialized, the various levers on the control consoles, must be operated to correspond to the condition of the simulated plant. Because of the multitude of such levers, and the many different sets of possible initial conditions, it is desirable that the instructor be able to determine quickly and accurately those devices on the control consoles which do not correspond to the applicable set of initial conditions. Thus, it is desirable for the simulator to detect any out-of-correspondence condition upon completion of initialization.
Further during simulation of the actual dynamic operation of the plant, the control devices where appropriate should cause the computer to operate the appropriate indicating device in the same manner and same real-time as the actual plant. The operation of some of these devices require an instantaneous response, while others necessitate a pattern of indication that can extend over long periods of time. For example, when switching on a pump, the needle on the appropriate indicating meter should respond instantaneously. In contrast, the operation of certain valves can take up to several seconds after the operation of the switch to indicate a fully operated position. A system as complex as a power plant has many changes occurring simultaneously through various parts of the process during transient conditions. At times when the simulated system is in a relatively steady-state, the number of sequential calculations in each repetitive calculation cycle is relatively minor. However, during start up, or under emergency or abnormal conditions, the number of calculations in each cycle becomes extreme. An effective power plant simulator should provide an instantaneous response, and render indiscernable to the operator the incremental changes occurring during each repetitive memory cycle; and at the same time, have a time interval of sufficient duration such that the calculation can be complete under all conditions prior to the end of each repetitive cycle or time step. A conventional method of accomplishing the foregoing is to provide a fast repetition rate, with the more active models being calculated at the higher rate, and some of the less active models being calculated at the slower rate. In some instances, this reconciliation does not permit as complete a simulation as is desired for the computers utilized. In known simulators utilizing a digital computer, with this type of arrangement the repetition rate or time step of the major active portions of the simulated plant is in the neighborhood of one-tenth of a second.
In addition to realistic real-time simulation, the simulators must be reliable and readily adaptable to program modification. It is also desirable that a portion of the plant simulator be capable of being operated, while another portion may be temporarily shut down for testing or modification.
It is desirable to use general purpose digital computers written in a program language, such as FORTRAN. This permits the building of a simulator that can use many types of computers, and the programs can be modified easily should the actual system being simulated be modified or changed. Also, it is desirable to achieve the instantaneous response, when required by the system, and to achieve the highest degree of realism in simulation, with a computer organization that has a calculation repetition rate or time step as slow as practicable while maintaining stability of operation. Further, the computer system organization should be such that a full-scope complete simulation of the nuclear power plant can be realized; and at the same time keep the computer space requirements and instructions to a minimum.
The foregoing desirable features can be achieved with a computer organization that performs periodic sequential calculations for some of the dynamic simulation, and performs other dynamic calculations on a demand basis only, with the additional capability of instantaneous response. The data should also be pre-processed prior to dynamic calculation and post-processed subsequent thereto, . to reduce the required calculations. The pre-processing and post-processing can be occurring at the same time as the dynamic calculations. It is also desirable to be able to use the same set of instructions for different data to conserve space in the computer.
Throughout all of the systems of a nuclear power plant are a multitude of fluid control devices, such as valves, pumps and manual/automatic controllers, for example. In simulating a system or subsystem, the effect of the operated condition of these devices must be considered in the calculations. In order to use the same set of instructions for different data and to reduce the number of calculations in the dynamic modeling, it is desirable to program the fluid control devices separately, so that only their ultimate affect on the simulation is entered prior to required dynamic calculations, and the data can be arranged in an optimum manner. Moreover, in order to isolate portions of the simulated system for testing and shutting down for repairs, it is desirable to utilize a plural computer organization. This further simplifies the programming by pre-processing data for panel logic or protective logic simulation likely, for example, in one computer prior to the transmission of the data for dynamic calculation to another computer. With such an arrangement the data processing can be carried on in both computers simultaneously. In a plural computer organization the synchronization of the functions of each computer becomes critical. It is desirable that the timing control means on each computer be operated such that no data will be transferred between computers, except at the proper time during each cycle.